The present invention relates to an information communication system represented by a duplex controller incorporating apparatus having a duplex controller to perform information communication between the first system and the second system.
Some recent disk array apparatuses construct a duplex controller incorporating apparatus having a duplex controller whose respective controllers can be connected to different host apparatuses. In a disk array apparatus of this type, data can be transferred between each controller (each system) and a corresponding host apparatus. Each controller has a cache memory for temporarily storing transfer data to the host apparatus.
Conventionally, a disk array apparatus (information communication system) having the above-described duplex controller employs a so-called mirrored cache scheme to increase the integrity of data on the cache memory in each controller (each system). In this scheme, write data received from the host apparatus by (the controller in) the self system is copied (mirrored) in the cache memory of the controller of the counterpart system.
In the disk array apparatus using this mirrored cache scheme, generally, after copy (write) in the cache memory of the counterpart system is completed, i.e., after the contents of the cache memory of the self system match those of the cache memory of the counterpart system, the host apparatus is notified of completion of the write.
Additionally, the disk array apparatus of this type generally has a special redundant path to improve reliability in important communication between the controllers.
As described above, in the conventional disk array apparatus (duplex controller incorporating apparatus or information communication system) having a duplex controller and using the mirrored cache scheme, the controller of the self system cannot return a completion message to the host side until the write in the counterpart system is ended, the write data communication path between the controllers becomes a bottleneck for write performance.
In addition, the conventional disk array apparatus (duplex controller incorporating apparatus or information communication system) must have a special redundant path to improve reliability in important communication between the controllers.